1. The Field of the Invention
This invention relates to electrodeposition of palladium; more specifically, this invention relates to the deposition of palladium at higher current densities than has heretofore been practicable with available prior art palladium baths and the obtention of higher efficiencies than heretofore observed when plating with conventionally available baths.
2. The Prior Art
It has been known from the prior art that palladium metal can be plated with various electrolyte bath compositions. While U.S. Pat. No. 2,027,358 teaches the deposition of palladium, such as from a double sodium nitrate salt in a solution which is slightly acid, this disclosure also indicates that, of various acids that can be used as an electrolyte, no particular acid or a salt has been revealed which would uniquely and synergistically increase the efficiency.
Thus, it has been a long sought goal to obtain a palladium deposit which could be used as a depost on a base metal at deposition efficiencies such as obtainable with other metals.
Other prior art, such as U.S. Pat. No. 3,530,050, discloses the plating of palladium employing a bath at a pH of 5 to 9 at a temperature from about 50.degree. to 95.degree. C. This disclosure further emphasizes the use of an ammonium salt of a weak organic acid suggesting specifically ammonium formate therefor. Current densities are from 2 to 400 ASF. As reported in this patent, the highest efficiencies are for the low current densities. These efficiencies are only about 85% to a current density of 6 ASF (amperes per square foot).
Other prior art which has been found such as published U.S. patent application No. B435,844, issued Jan. 28, 1975, though it contains a profusion of disclosure of various electrolytes, it fails to disclose the particular combination of elements being claimed herein.